The present invention relates to a lens hood, particularly to a lens hood suitable for use on camera lenses.
Camera lenses are usually supplied with a lens hood for shielding rays of light coming from outside the picture area, or outside the angle of view of the lens, and it is mounted at the front end of the lens barrel. In order to enhance the photographic effect of a camera lens, it is also common practice to mount a polarizing filter, crossed filters and various other filters at the front end of the lens barrel. In the case of a polarizing filter, the position of its rotation about the optical axis is changed to limit the amount of polarized light from the subject so as to produce a sharper picture. In the case of crossed filters, the position of their rotation about the optical axis is changed to alter the direction of a blurred cross. These filters that create varying photographic effects by changing the direction of rotation about the optical axis are hereunder referred to as "rotatory effect filters". If they are used on a single-lens reflex camera, their effectiveness can be confirmed by looking through a viewfinder and, therefore, the aforementioned lens hood which is to be mounted at the front end of the lens barrel is so adapted that pictures can be taken with the lens hood attached to the lens barrel and as those filters are rotated.
FIG. 15 is a partial section of the lens hood used in combination with a polarizing filter as a rotatory effect filter. The polarizing filter generally indicated by 20 comprises a movable frame 22 that supports the rim of a disk-shaped optical filter glass 24 and a fixed frame 21 which supports said movable frame 22 in such a way that it can rotate about the optical axis. Said fixed frame 21 has a male thread 23 formed on the outer periphery and by bringing it into engagement with a female thread 11 formed on the inner periphery at the front end of a lens mount 10, the fixed frame 21 can be fitted on the lens mount 10. Once the fixed frame 21 has been fitted, the movable frame 22 can be rotated relative to said fixed frame 21 so that the rotation of the polarizing filter 20 about the optical axis is adjustable to a desired position. A lens hood 30A is fitted around the front end of the lens mount 10 and it may be of a bayonet type.
In order to ensure that the rotatory effect filter, which is the polarizing filter 20 in the case under consideration, can be rotated with the lens hood 30A fitted on the lens mount 10, the lens hood 30A is formed to have a sufficiently larger outside diameter than the lens mount 10 that a wide enough space to permit the passage of fingertips of a photographer is formed around the polarizing filter 20. When taking pictures with the polarizing filter 20 fitted in the lens hood 30A, the photographer puts the finger into the lens hood 30A through the front opening and rotates the polarizing filter 20 relative to the lens mount 10 by manipulating the movable frame 22 with the finger.
A problem with the lens hood 30A is that while the photographer manipulates the polarizing filter 20 with one hand while looking at the subject through the viewfinder, the hand which has been put into the lens hood 30A through the front opening hides a portion of the lens mount 10 to cause occasional vignetting in the field of view and this is by no means desirable for the purpose of checking for the appropriateness of the picture area. As a further problem, in order to ensure the space through which the finger can be put into the lens hood 30A, its outside diameter is prone to be unduly larger than that of the lens mount but this is not desirable from portability and design viewpoints.
To solve this problem, the idea shown in FIG. 16 was proposed; an opening 35 or a hole through which a photographer's finger can be put into a lens hood 30B is made in a selected area of the lens hood 30B and the photographer manipulates a polarizing filter 20 by rotating it via the opening. With this lens hood 30B, there is no need to provide a space around the polarizing filter 20 into which the finger can be put and this not only reduces the outside diameter of the lens hood 30B but also prevents the field of view through the viewfinder from being blocked by the photographer s hand with which the polarizing filter 20 is being adjusted. On the other hand, however, when the photographer removes the finger out of the lens hood 30B and performs the actual shooting by, for example, releasing the shutter, rays outside the angle of view will get into the lens mount 10 through the opening 35 and the intended function of the lens hood is not fulfilled.